Just say no. Please, Marissa. Just. Say. No.

We may well look back and see that CES 2014 was the moment when Marissa Mayer’s honeymoon period as Yahoo’s new CEO began to end.

Sure, she was on stage confidently announcing new products in front of the world’s tech press. There wasn't an empty seat in the house, and it was Mayer's biggest appearance as head of Yahoo to date.

But behind the scenes, the picture was far less put together. Her senior team was in disarray. Traffic for her $1.1 billion play at wooing fickle teens was fading. Her pricey splash into real journalism was getting rerouted into a division of marketing.

We’re about 18 months into Mayer’s regime as Yahoo’s CEO. And the biggest move she's made was one of her first, and it was four CEOs in the making: Finally unlocking the Alibaba assets shareholders kept asking for. That’s still the biggest thing keeping the stock afloat. Is that really all there is going to be to one of the most anticipated turnarounds in the history of the Web?

Mayer is in that very, very rarified air of Silicon Valley leaders that get the benefit of the doubt. Sure, she has haters. But they are largely of the 20-year-old sniveling gossip blogger variety or people who freak out about logos. When it comes to Wall Street, when it comes to potential board members, when it comes to would-be acquisition targets, when it comes to her peers in the Valley – you know, all the people who actually matter when you are trying to turn around a company that no one has yet been able to turn around – they’ve all given her more than a year of benefit of the doubt.

We've heard it at PandoMonthly after PandoMonthly: If anyone can do it, Marissa can. Everyone has wanted to believe. This rare and sweeping benefit of the doubt – greater even than what Tim Armstrong got when he took the reins of AOL – was why Marc Andreessen’s immediate reaction was to call it a no brainer career move for Mayer. Either she fixes it, in which case, she's one of the great CEOs in Internet and Valley history. Or she doesn't, and the meme is that Yahoo is so broken even Marissa couldn't fix it.

But there’s a third option that may be playing out: She’s fixed the stock, largely through that Alibaba deal. But, again like her fellow Xoogler Tim Armstrong, she still hasn’t fixed the company. Not by a long shot. In fact, she may have taken the things that ailed Yahoo – a distracted, bloated focus across dozens of products and industries where it was good but not great – and made that problem worse.

Every great CEO will tell you the hardest part of their job isn't say yes. It's saying no. And Mayer has seemed incapable of it. That was especially bad given that Yahoo was a number two player in a cascade of silos. It was exactly the company that needed a long series of No's.

I defy anyone to look at the last 18 months and articulate a strategy of discipline and focus.

Let’s review.

While everyone started out hoping for a big YouTube-like purchase -- someone surging like a Pinterest – Yahoo instead bought Tumblr.

Tumblr is great. But fairly or not, it's known as the company that couldn't ever seem to build a business off its runaway consumer success. In other words, it was seen as a company that was all to happy to sell as long as the price and terms were good enough. It wasn't an Instagram or even a YouTube. It was a “win” for Tumblr and it’s shareholders, no doubt. But Yahoo displayed little more than an ability to write a bigger check and make credible promises that Tumblr would be left alone.

The Tumblr deal was buffeted by a wide, dizzying, and confusing array of mid-priced deals and acqui-hires. Mayer had convinced people selling to Yahoo was cool, but she was also playing a welcome role in the Valley, practically single-handedly solving the series A crunch. There are worse ways to inject huge amounts of entrepreneurially-minded engineering talent into your company, no doubt. But even Mayer's boosters couldn't argue with a straight face that this all seemed to make sense within a single cohesive strategy.

At the same time she was on frantic buying spree through Silicon Valley's bargain aisle, she spent some significant cash bolstering Yahoo's original editorial and content divisions-- one of the areas of the company that many people assumed Mayer would cut wholesale. After all, she was a product person from Google. If Yahoo wanted to be a content media company, why not give the job to Ross Levinsohn?

Instead, she hired big (expensive) names like David Pogue and Katie Couric and did a big splashy announcement of Pogue's new tech site at CES. But behind the scenes, that division was in turmoil. Mayer was in the process of firing her number two Henrique De Castro, and reorganizing the media unit to report to…. marketing. Exactly what any journalist who has taken a gamble on a CEO who doesn’t have a track record of understanding journalism wants to hear. That news was followed swiftly by the reports that Jai Singh, Yahoo’s Editor-in-Chief and the only senior guy who actually knew something about content was also leaving.

Even when Mayer is saying no, she’s saying yes. De Castro received a gargantuan $109 million payout, despite lasting just 15 months on the job. It was called one of the biggest golden parachutes in corporate history. The payout was despite it being quite clear that Mayer was unhappy with De Castro’s performance. Kara Swisher says the reasons behind De Castro’s unceremonious exit will become even clearer at Yahoo’s upcoming earnings call.

In other words: We’re not done here. Anyone else getting chilly? Because there's a massive snowball forming on the horizon.

And, now Forbes reports today that Tumblr's traffic isn't growing. Yahoo says that comScore isn't taking mobile into account, and that may well be true. But ask any of the previous CEOs who've tried to turn around Yahoo: Facts don't matter nearly as much as perception in the face of a snowball.

If people aren't losing confidence in Mayer after the bizarre grab-bag shopping spree, the zig-zagging on original content, and the sudden booting of two top recruits, it's not going to take too many more gut punches like the one Forbes-delivered today to push them over the edge.

I know that the Valley wants desperately to believe someone can turn around an ailing consumer Web giant. And I know the Valley loves to root for Mayer in particular. But we can only give someone so much benefit of the doubt. Mayer may be a legend in the Valley, but she’s still a first time CEO, and the first time CEO of a company that has made four previous CEOs look like clowns. Let's hope giving De Castro the boot is the beginning of some hard decisions at the purple giant.